Using the sum of the interior angles of a triangle | Maths

Starter quiz

The sum of 241, 68 and 192 is ______.

'501' ✓
Simplify the following expression $3x+5y-2x+9y+3x+12$ .

$8x+14y+12$

$8x-14y+12$

$4x+14y+12$ ✓

$4x-14y+12$

$18xy+12$
A triangle DEF, where DE = 23 cm, DF = 23 cm and angle EDF is 45° is __________ triangle.

a scalene

an isosceles ✓

an equilateral

a right-angled scalene

a right-angled isosceles
Solve $29=54-2x$

$x=12.5$ ✓

$x=-12.5$

$x=41.5$

$x=83$

$x=25$
Which of these are correct for the size of the angle marked $n$ ?

$n=28$

$n=180-(28+131)$ ✓

$n=131$

$n=180-28-131$ ✓
Select the statements that best complete the following sentence. By tearing the corners off of a triangle and arranging them together at a point it you have...

...shown that the three angles in a triangle sum to 180°. ✓

...demonstrated that the three angles in a triangle sum to 180°. ✓

...proved that the three angles in a triangle sum to 180°.

The size of the angle $x$ ° is ______°.

'38' ✓
Match the two angles of a triangle with its third angle.

60°, 60°

⇔

60° ✓

57°, 103°

⇔

20° ✓

90°, 27°

⇔

63° ✓

108°, 51°

⇔

21° ✓

51°, 98°

⇔

31° ✓

104°, 38°

⇔

38° ✓
In which of these triangles is there enough information for you to calculate the size of the missing angle?
The size of the angle $x°$ is ______°.

'78' ✓
Which of the following are calculations to find the value of $y$ ?

$y=\frac{180+28}{2}$

$y=\frac{180-28}{2}$ ✓

$2y=\frac{180-28}{2}$

$y=\frac{1}{2}(180-28)$ ✓
Work out the value of $m$ .

10

12 ✓

60

180

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Missing angles in triangles can be found using the angle sum.
Missing angles in triangles can be found using the angle sum and other triangle properties.

Assuming triangles are certain types because of how they look.

Unless there is notation or it has stated the type of triangle you cannot assume.